FI128009B - Arrangement and method in a soda recovery boiler - Google Patents

Abstract

Arrangement and procedure in a soda pan. The soda boiler (100) comprises a second feature (9), in which second feature (9) is provided at least one superheater (4 ') and the second feature's ash funnel (14), the front and / or rear wall (15) of the ash funnel (14). , 16) is coupled to the boiler (100) steam cycle.

Description

The invention relates to an arrangement in a recovery boiler.

The invention further relates to a process in a recovery boiler.

In the pulp production process, black liquor is burned in a recovery boiler.

The duties of the recovery boiler include the recovery of chemicals and the recovery of thermal energy from combustion.

The soda boiler has a furnace to supply black liquor and combustion air. There are superheaters at the top of the boiler, and after the superheater area there are 10 flue gas ducts. The flue gas duct has a cooking surface and economizers. The thermal energy generated by the combustion produces superheated superheated steam, which can be used, inter alia, in power generation.

When it is desired to raise the temperature of the superheated steam, some of the superheaters may be fitted to a second draft, i.e. the first channel section of the post-boiler flue gas channel en15. As a result, the temperature of the surfaces of the second draw may increase too much.

WO 2014/044911 A1 discloses an arrangement in which a second draw is arranged to be cooled by a cooling medium from the curtain piping forming part of the boiler water cycle.

Short description

The arrangement and method of the invention in a recovery boiler is characterized by what is stated in the characterizing parts of the independent claims. Other embodiments of the invention are characterized by what is set forth in the other claims.

Inventive embodiments are also disclosed in the specification and drawings of this application. The inventive content contained in the application may also be defined otherwise than as set forth in the claims below. The inventive content may also consist of several separate inventions, especially if the invention is considered in the light of the express or implied subtasks or in terms of the benefits or classes of benefits achieved. Thus, some of the attributes contained in the claims below may be redundant for individual inventive ideas. Aspects of various embodiments of the invention may be applied in conjunction with other embodiments within the scope of the inventive concept.

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In the arrangement according to the invention, the front and / or rear wall of the second draw of the ash hopper of the recovery boiler is connected to the steam circulation of the recovery boiler. The advantage is that the second draft in the hot area can be effectively cooled and heat from the flue gas can be transferred to superheat steam.

In the method of the invention, the second draw is cooled by introducing steam into the front and / or rear wall of the ash hopper of the second draw. The advantage is that the temperature of the second draw can be controlled efficiently and simply.

The following is a list of features of some embodiments of the invention in random order. The characteristics of the process in question determine which embodiment is most advantageous in each case.

The idea of one embodiment is that the cylinder of the recovery boiler is connected directly to the front and / or rear wall to supply steam.

The idea of one embodiment is that the cylinder 15 of the recovery boiler is indirectly connected to the front and / or rear wall for supplying steam.

The idea of one embodiment is that the furnace furnace furnace, before the superheaters, is provided with a steam curtain piping connected to the front and / or rear wall of the ash hopper to supply steam.

The idea of one embodiment is that the fire chamber 20 of the recovery boiler comprises a furnace roof superheater connected to the front / or back wall of the ash hopper to supply steam.

The idea of one embodiment is that the second draft ashtray comprises an ashtray roof superheater connected to the front and / or rear wall of the ashtray to supply steam.

The idea of one embodiment is that the ash hopper rear wall is connected to the steam circulation in series such that the steam is arranged to be fed from the ash hopper front wall to the rear wall or vice versa.

The idea of one embodiment is that the ash hopper rear wall is connected to the steam circulation in parallel so that only a portion of the steam delivered to the front and rear wall is supplied to each of them.

The idea of one embodiment is that the front wall of the ashtray is connected to a steam circulation and the rear wall is water-cooled.

The idea of one embodiment is that the rear wall of the ashtray is integrated into the front wall of the cooking surface which is connected to the water circulation.

The idea of one embodiment is that the steam is adapted to be fed from the front and / or back wall of the ashtray to the side wall of the second draft.

20145866 prh 25 -03- 2019

The idea of one embodiment is that the steam is adapted to be fed from the front and / or back wall of the ashtray to the side wall of the second draft and further to the suspended superheater fitted inside the second draft.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, in which Fig. 1 is a schematic side and partially sectional view of a recovery boiler; Figure 5 is a schematic view of another side and partial sectional view of a second draft of another recovery boiler, and Figure 6 is a schematic view of a third side and partial sectional view of a second draft of the recovery boiler.

In the figures, the matter is simplified for clarity. Like parts are denoted by like reference numerals in the figures.

Detailed description

Figure 1 schematically shows a recovery boiler from the side and partly in section. The soda boiler includes a furnace 1 for supplying black liquor for combustion through the nozzles 2. The combustion air is supplied to the furnace 1 via the air nozzles 3.

Superheaters 4 are provided in the upper part of the furnace furnace furnace 1. The superheaters 4 are elements formed by a plurality of parallel vertical pipes which are arranged in parallel in the transverse direction of the recovery boiler. Steam in the superheaters, which heats up as hot flue gases heat the pipes from the outside.

The recovery boiler may comprise a cam 6 for controlling the flow of flue gases.

After the upper part of the furnace 1 and the second draft 9, the flue gases hate the convection heat surfaces 8, which comprise successive duct sections which are connected at their ends.

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The second draw 9 is provided with superheaters 4 '. These superheaters 4 'increase the temperature of superheated steam compared to the solution where only superheaters are located at the top of the recovery boiler.

The walls 5 and superheaters 4, 4 'of the boiler are so-called. heat transfer surfaces. These thermal surfaces either have spaced tubes or are formed by welding gas-tight walls such as boiler walls 5.

The second draw 9 comprises an ash hopper 14 for collecting chemicals and ash and for removing them from the second draw 9.

The ash hopper 14 comprises a cooled front wall 15 and a cooled rear wall 16 for lowering the temperature of the ash hopper 14 surfaces. The structure and function of the cooled front and rear walls 15, 16 will be discussed in more detail below. The cooled front and back walls can lower the temperature of the ash hopper surfaces to reduce their risk of damage.

Convection heat surfaces 8 after the second draw 9 typically have additional heat surfaces, for example known cooking surfaces 10 and economizers 11.

The recovery boiler further comprises a water and steam system. This 20 includes a cylinder 12 for supplying hot water and steam to the heating surfaces of the recovery boiler. In the embodiment shown in Figure 1, the cylinder 12 is directly connected to the front and rear walls 15, 16 for supplying steam as shown below.

The cooling tubes of the ash hopper 14 front and rear wall 15, 16 form a closed structure at the bottom of the hopper, an example of which is shown in Figure 3a. Said cooling pipes are grouped higher into front wall lattice piping 18 and rear wall lattice piping 19. The lattice piping 18, 19 comprises spaced apart and at least substantially vertically arranged pipes from which flue gas can flow forward. An example of a cross section of a lattice pipe is shown in Figure 3b.

Front wall lattice conduit 18 is connected to cylinder 12. Steam 12 directs steam to cooling conduits of front wall 15, from where it is further conducted through cooling conduits of rear wall 16 to rear lattice conduit 19 and from there to superheat step. In other words, the cooling pipes of the front and rear walls 15, 16 are connected in series to the steam circulation of the recovery boiler 100.

In another embodiment, the cooling tubes of the ash hopper front and rear walls 15, 16 are connected in series to the steam circuit so that the steam

20145866 prh 25 -03-20199 are fed first to the cooling pipes of the rear wall 16 and then to the cooling pipes of the front wall 15, i.e. unlike Figure 1.

According to one idea, the cooling pipes of the front and rear walls 15, 16 may be divided into parallel circuits so that the steam is conducted into one of these cycles, after which the steam passes through the parallel circuits before being passed to the next superheat step.

By cooling the front and rear walls, the temperature of the ash hopper 14 can be kept so low that, for example, thermal expansion does not cause any problems. In addition, heat energy is transferred to steam, i.e. 10 increases the energy content of the steam, which contributes to e.g. to achieve a higher final steam temperature. Now, for example, steam having a final temperature of 515 ° C can easily be provided.

It should also be noted that, to simplify the presentation, not all of the pipes and chambers of the water and steam system 15 associated with the thermal surfaces are shown in the accompanying figures. However, in practice, several downpipes may be led to each heating surface and multiple circulation tubes may be led from the thermal surface to the cylinder. Further, it should be noted that the term "steam" may include both saturated and superheated steam.

Fig. 2 schematically shows a detail of the recovery boiler in side and partly in section.

An arrangement and method are shown wherein cylinder 10 of the recovery boiler is indirectly connected to the front and / or rear wall 15, 16 of the ash hopper for supplying steam. In the illustrated embodiment, a steam curtain pipe 7 is connected to the furnace furnace furnace 1, before the superheaters and at the nozzle 6, which is connected to the front and rear walls 15, 16 of the ashtray 25. The steam curtain pipe 7 is fed with steam from It should be noted that cylinder 12 is not shown for simplicity of presentation.

The steam curtain piping 7 comprises heating surface tubes 28. In the heating surface tubes 28, steam flows which is heated by the effect of the flue gases flowing past. Correspondingly, this causes the temperature of the flue gases to drop before they reach the superheaters 4. In addition, the steam curtain pipe 7 protects the superheaters 4 from direct radiation from the furnace.

The steam curtain pipe 7 is connected by one or more connecting pipes 17 to the cooling pipes of the front and rear wall 15, 16 of the second draft ash hopper 14.

That is, the cooling tubes of the second draw ash hopper 14 are connected to the left

20145866 prh 25 -03-20199 to recover steam from the curtain piping 7. The steam may be led after the cooling pipes of the front and rear walls 15, 16, for example, to a thermal surface.

Figure 3a shows a first cross-section 5 of an ashtray, and Figure 3b a second cross-section.

In the cross-section shown in Fig. 3a, the cooling tubes 25 connected to fins 27 form gas-tight front and rear walls of the ashtray 14. Such a structure can be manufactured, for example, by welding. Of course, the gas-tight structure may be formed in other ways, for example by directly connecting adjacent cooling tubes 25 to one another. On its sides, the ash hopper 14 is limited to the side walls of the second draw 9.

At the top of the ash hopper 14, the cooling tubes 25 are grouped in a lattice shape into a front wall lattice pipe 18 and a rear wall lattice pipe 19. One cross-section of the lattice shape is shown in Figure 3b. Of course, the grid shape can also be such as long as the cooling pipes 25 are loosely arranged to allow the flue gases to flow through.

Fig. 4 schematically shows a side view of a second draft of the recovery boiler and a partially cut away view.

The second draw 9 comprises a second draft roof supercharger 22 fitted to the steam circulation of the recovery boiler 100 by connecting it in series with the cooling pipes of the front and rear walls 15, 16 of the ash hopper 14. For example, steam is introduced from cylinder 12 - not shown in the figure - to the front wall 15 of the ash hopper, and further to the rear wall 16 of the ash hopper and thence to said second draft roof supercharger 22.

In another embodiment, the steam is conducted in the opposite direction as above, i.e. from the rear wall 16 of the ash hopper to the front wall 15 and thereafter to a second draft into the roof superheater 22.

According to one idea, the second draft roof superheater 22 is connected 30 only to the ash hopper front wall 15 or the ash hopper rear wall 16, for example, the second draft roof superheater 22 may be connected to the ash hopper front wall 15 while the rear wall 16 is cooled by water circulation.

Fig. 4 shows a broken line of a furnace roof superheater 23 fitted to the furnace 1 of the recovery boiler. This can be connected to the front 35 and / or the rear wall 15, 16 of the ash hopper 14 as a second draft roof supercharger 22.

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The 100 may of course comprise both roof superchargers 22, 23, both of which may be connected to the front and / or rear wall 15, 16 of the ash hopper 14.

In addition to the aforementioned couplings, the side walls 26, or at least one of them, of the second draft may be connected to the ash hopper front / rear wall 15, 16 and / or the roof superheaters 22, 23.

Fig. 5 schematically shows another construction of the second draw of the recovery boiler in a side and partially sectional view. Here the front wall 15 of the ashtray is connected to a steam circulation. The steam is led from the ash hopper front wall 15 to a heating surface, for example to a second draft sidewall 26. The ash hopper 14 does not have its own separate rear wall 16, but is replaced by a cooking hob front wall 24. This can also be expressed by integrating the ash hopper , 24 connected to the water circulation, that is, water cooled. The water can be led from the cylinder 12 along the drain pipe 13 to the lower part of the ash hopper 14 and from there up to the front wall 16, 24 of the cooking surface, where it evaporates.

The integrated wall 16, 24 is reconnected to cylinder 12 or to a thermal surface.

At least one of the side walls 26 of the second draw 9 may be in a vapor circulation, i.e. steam cooled, and may be connected to the front wall 15 of the ashtray.

Fig. 6 schematically shows a third side view of a second draft of the recovery boiler, partially and partially broken away.

The steam that cools the second draft 9 is first introduced into the gutter piping 18 of the ash hopper front wall, then down through the front wall 15 to the rear wall 16 and further up the back wall gutter piping 19.

The rear wall lattice conduit 19 is connected by one or more rotation tubes 20 to at least one second draft sidewall 26. The steam may travel up and down the second draft sidewall 26 so that the vapor flow is optimized for, for example, steam velocity and / or pressure drop.

The steam may be supplied from the side wall 26 of the second draw to a thermal surface. An embodiment of the latter alternative is shown in dashed lines in Figure 6. Here, the steam is fed from the side wall 26 of the second draw into a hanging superheater 21 fitted inside the second draw 9, and further to a heating surface.

In some cases, the features set forth in this application may be used as such, despite other features. On the other hand, the features disclosed in this application may be combined, if necessary, to form different combinations.

The drawings and the description related thereto are only intended to illustrate the idea of the invention. It will be apparent to one skilled in the art that the invention is not limited to the embodiments described above, in which the invention is illustrated by some examples, but many modifications and various embodiments of the invention are possible within the inventive concept defined in the claims below.

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The reference numbers

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4, 4 '

100 furnace mustalipeäsuutin air nozzle heating surface wall cam steam curtain pipes konvektiolämpöpinta second drive cooking surface economiser cylinder tube or the steam tube of the second strain ash hopper ash hopper front wall of the ash hopper back wall of the connecting tube of the front wall tube bank of the rear wall of the tube bank of the circulation pipe hanging superheater another bet another bet kattotulistin furnace kattotulistin rear wall or the cooking surface of the front wall of the cooling tube of the second wager side wall of the fin heating surface tube recovery boiler steam flow water flow

Claims (5)

An arrangement in a recovery boiler, the recovery boiler (100) comprising a second stroke (9), wherein the second stroke (9) is provided with at least one superheater (4 ') and a second stroke ash hopper (14), characterized in that and / or the rear wall (15, 16) is connected to the upper part of the cylinder (12) of the recovery boiler (100) and thus to the steam circulation of the recovery boiler (100) and to receive superheated steam. 10 An arrangement according to claim 1, wherein the recovery boiler cylinder (12) is connected directly to the front and / or rear wall (15, 16) for supplying steam. An arrangement according to claim 1, wherein the cylinder (12) of the recovery boiler 15 is indirectly connected to the front and / or rear wall (15, 16) for supplying steam. Arrangement according to claim 3, wherein a steam curtain pipe (7) is arranged in the furnace furnace furnace (1), before the superheaters, which is 20 connected to the front and / or rear wall (15, 16) of the ash hopper (14) for supplying steam. An arrangement according to claim 3, wherein the furnace furnace furnace (1) comprises a furnace roof superheater (23) connected to an ashtray 25 lon (14) to the front and / or rear wall (15, 16) for supplying steam. An arrangement according to claim 3, wherein the second draw ash hopper (14) comprises an ash hopper roof supercharger (22) coupled to the front and / or rear wall (15, 16) of the ash hopper (14) for supplying steam. An arrangement according to any one of the preceding claims, wherein the front and rear walls (15, 16) of the ash hopper (14) are connected in series to the steam circulation so that steam is arranged to be fed from the front wall (15) of the ash hopper (14) to the rear wall (16). 20145866 prh 25 -03- 2019 An arrangement according to any one of claims 1 to 6, wherein the front and rear walls (15, 16) of the ash hopper (14) are connected to the steam circulation in parallel so that only a portion of the steam supplied to the front and rear walls (15, 16) is fed to each. An arrangement according to any one of the preceding claims, wherein the front wall (15) of the ashtray (14) is connected to a steam circulation and the rear wall (16) is water-cooled. An arrangement according to claim 9, wherein the rear wall (16) of the ashtray is integrated with the front wall (24) of the cooking surface which is connected to the water circulation. An arrangement according to any one of the preceding claims, wherein the steam 15 is adapted to be fed from the front and / or back wall (15,) of the ash hopper (14). 16) a second draw to the side wall (26). An arrangement according to claim 10, wherein the steam is adapted to be fed from the side wall (26) of the second draft into the second draft (9). 20 fitted to the suspended superheater (21). A method in a recovery boiler comprising: a second stroke (9), at least one superheater (4 ') fitted to the second stroke (9), and A second draw ash hopper (14), characterized in that the method cools the second draw (9) by introducing steam into the front and / or rear wall (15, 16) of the second draw ash hopper (14) for superheat. A method according to claim 13, wherein steam is fed directly from the cylinder (12) of the recovery boiler directly to the front and / or rear wall (15, 16) of the ash hopper (14). A method according to claim 13, wherein steam is supplied from a cylinder (12) of the recovery boiler through a heating surface of a second draft ash. 35 on the front and / or rear wall (15, 16) of the hood (14). A method according to any one of claims 13 to 15, wherein steam is fed directly from the front and / or rear wall (15, 16) of the ash hopper (14) into the cylinder (12) of the recovery boiler. A method according to any one of claims 13 to 15, wherein steam from the front and / or back wall (15, 16) of the ash hopper (14) is fed to a thermal surface of the recovery boiler (100).